Overshoe heel



Jan. 8, 1963 F. R. LAPORTE 3,071,817

' OVERSHOE HEEL Filed Aug. 14. 1959 INVENTOR. fE/MMfl A. 14/ 0/275ATTORNEY weight of a woman would be supported small surface.

astral? l atented Jan. 8, 1.963

" Flee 3,071,817 OVERSHOE HEEL Fernand R. Laporte, St. Jerome, Quebec,Canada, asslgnor to United States Rubber Company, New York, N.Y., acorporation of New Jersey Filed Aug. 14, 1959, Ser. No. 833,828 2Claims. (Cl. 18-58) This invention relates to an overshoe having areinforced inner heel base and to a method for making such a heel base.

The widespread adoption of the spike or French heel on womens footwearhas been a source of trouble to the manufacturer of womens overshoes.This heel is charracterized by the fact that its cross-sectional areabecomes narrower and narrower from the top of the heel to the base. Forexample, the heel shank may taper downwardly so that its bottom surfaceor tip may be only one quarter of an inch across. Thus, during walking,the entire by this very When overshoes are placed over a shoe having aFrench heel, extremely high stresses are exerted on the overshoe heelportion, and considerable wear results where the heel contacts theovershoe. In fact, the French heel is so narrow that it acts as a spikeand punches a hole in the overshoe heel base.

Punching is not the only problem caused by wearing a French heel.Cracking or rupturing along the lower sidewalls of the overshoe alsooccurs. This cracking is due in part to the excessive stresses placed onthe overshoe by the French heel, and in part to shockthe suddenness withwhich such stresses are applied. It is a common fact that more wearoccurs at a surface which is subjected to a repeated, sharp stress thanat a surface to which the stressis applied gently.

Attempts to overcome such problems have only been partially successful.In a patent granted October 14, 1930, No. 1,778,592, a flat plate havingturned edges is inserted in the heel of a ladies overshoe to overcomethe wear problems associated with the French heels. Other patentees haveproposed more elaborate wearplates having vertical side surfaces as wellas a bottom surface. As shown in Patent No. 1,119,277 granted December1, 1914, and Patent No. 2,108,572 granted February 15, 1938, such wearplates are inserted into the hollow heel portion of r the overshoe.

It has been found that the heel of the overshoe still wears through whenthe aforementioned wear plate attachments are inserted into the heel.Friction, and wear which necessarily accompanies the friction, remainsbe tween the inner side of the overshoe and the surface of theattachment in contact therewith. Further, the attachment can easily bekicked from its proper position.

Since the overshoe is not a rigid body, there is always some latitude infitting the attachment to the heel. If the overshoe fits too snuglyabout the attachment, excessive sress develops along the overshoesurface that grips the attachment, eventually causing a wearing throughor a cracking of the overshoe wall.

Also, these attachments do not provide by themselves a cushioningeffect. Each step taken produces a sharp, concentrated pressure that istransmit-ted through the wearplate to the overshoe surface. Recognizingthis problem, cushioning pads have been employed in the past, as shownin the aforementioned Patent No. 2,108,572. However such pads wear outrapidly and do not readily remain in a fixed position.

In addition, wearplates generally present a slippery surface to theheel. The French heel could not remain in one position durink walkingwith respect to the overshoe heel since it is much narrower than theovershoe heel and slides over the wear-plates. This sliding action tendsto move the wearplates, increasing the friction between the inner sideof the overshoe and the wearplate surface in contact therewith.

One object of this invention is to provide a method for making anovershoe heel that will not be punctured or ruptured when used withshoes having narrow heels.

Another object of this invention is to provide a method for making areinforced overshoe heel having an integral reinforcing lining ofrelatively high wear resistant material as compared with the material ofthe overshoe.

A further object of this invention is to provide a method for making areinforced overshoe heel having an inner layer that will keep a narrowheel in a fixed position and will tend to eliminate heel slipping.

A still further object of this invention is to provide a method formaking an inner reinforcing layer in an overheel that will cushion thepressures that are applied to I the overshoe heel during walking.

In order to provide an overshoe having a reinforced heel base andsidewalls, this invention contemplates a lining of relatively highabrasive material molecularly bonded to the inner surface of the heelbase and sidewalls; the layer will extend across the base of the heeland up along the sidewalls thereof. An integral heel will thus be formedwhich eliminates the aforementioned problems associated with looseattachments.

To accomplish these objectives, during the production of the shoe, aquantity of viscous liquid plastic material is poured into the heel ofthe shoe to the height desired of the sidewall layer and heat is appliedto the plastic material. A suction tube is then inserted into this bodyof plastic and the central portion or core portion is sucked up. Thesidewalls remain because the heat has gelled the layer of plasticadjacent the walls of the shoe.

The above and other features of the instant invention will be furtherunderstood from the following description when read in conjunction withthe accompanying drawing, wherein:

FIG. 1 is a sectional view of the heel showing the reinforcing liningmolded or bonded to the inner overshoe surface;

FIG. 2 is a sectional view of the overshoe heel and shows the heelfilled with a quantity of highly viscous liquid plastic and also showsthe suction tube being placed in the liquid;

FIG. 3 shows the suction tube positioned in the tube and illustrates theviscous plastic being drawn up; and

FIG. 4 shows the formation of the viscous plastic in the heel just afterthe suction tube is removed and illus trates the application of heat tothe heel and the gelled plastic reinforcing unit.

An article of rubber-like footwear 10 is shown in FIG. 1 have a heel 11and walls 12. This article can be an overshoe or gaiter having plasticwalls formed by conventional slush molding methods. The plastic materialused to produce such slush molded footwear is preferably a vinylplastisol prepared by dispersing finely divided polyvinyl resin powderin a liquid plasticizer. The reinforcing heel unit 13 is also aplastisol'but is compounded so as to be more resistant to wear than theplastic overshoe walls 12.

The reinforcing heel unit 13 has the same shape as the inner heel walland is therefore adapted to receive the heel of a shoe. The preferredembodiment is described with reference to womens footwear and thereforethe shank of heel 11 is relatively long. The heel'unit 13 comprises abottom layer 14 and sidewalls or upright layers 15, joined together.This unit is molecularly bonded or fused at bonding surface 17 to theinner surface of the overshoe wall to provide an integral reinforcingheel unit. That is, because of heat treatment, the plastic overshoewalls and reinforcing layers coalesce to form an integral mass of singlephase plastic material. In effect, there is no bonding surface 17 asthat surface becomes part of a continuous medium.

The reinforcing heel unit thus described is not a rigid body and tendsto be shock absorbing. Further the top or open surface of this unitwhich is in contact with the Womans shoe heel presents a high frictionsurface as opposed to metal, or the synthetics such as nylon.

The particular thickness of each layer and the height of the sidewallscan be varied as desired. The following dimensions have been employed inthe preferred embodiment and are given here by way of example: the basethickness 18 may be .200 to .250 of an inch; the sidewall height 19 fromthe inside of the wall base may be .625 of an inch; the thickness 20 ofthe sidewall 15 may be 050-070 of an inch.

A description of the method of making a reinforced heel unit in aplastic overshoe is given hereinbelow. It is well known to those skilledin the art to make rubberlike or plastic footwear by slush molding. Incarrying out this method, a hollow mold is used which has an interiorsurface that defines the exterior contours of the footwear. Liquidplastic material is then poured into the mold to a predetermined depth.Heat may be applied to the mold either before or immediately after theplastic material enters the mold.

The plastic material used herein has the physical characteristics of aheavy, viscous cream-like consistency in its uncured state. This plasticmaterial is cured by the application of heat which changes the viscousliquid into an elastic-like material. Since the duration of the heatcontrols the amount of elastic-like material that is formed, the heatingcan be controlled over certain preselected areas when a particularthickness is desired. As heretofore stated, the plastic material used toproduce such slush molded footwear is preferably a vinyl plastisol,prepared by dispersing finely divided polyvinyl resin powder in a liquidplasticizer therefor to for a creamy liquid. The slush molding techniqueand the preparation of plastisols is further discussed in Patent No.2,880,467 to V. l. Wibbens granted April 7, 1959.

in making an overshoe by slush molding, a metal mold Zia is filled tothe desired height by the liquid plastic. Heat is applied to the metalmold 21a to cause the plastic material that contacts the metal wall toadhere thereto. The adhering plastic layer is only a gelled film sincethe plastic is not completely cured. When the thickness of this film issufficient, the rest of the liquid plastic is poured from the mold andthe overshoe is entirely fused thereafter while still in the mold by thefurther application of heat.

Fusion takes place when the temperature is raised above the softeningpoint of the resin, at which temperature the solvent action of theplasticizer is increased to cause the resin and plasticizer to form atough homogeneous resinous mass in which the powdered resin and theliquid plasticizer have coalesced to form a single phase.

The method of this invention contemplates pouring a quantity of viscousplastic into the heel cavity of the overshoe before the plastic isfinally cured or fused. As shown inFIG. 2, the heel is filled withviscous plastic 20 to the desired sidewall height. The overshoe remainsin the mold that has already been heated, so heat is applied to theviscous plastic to some extent. That is, the heat that has been appliedto the mold to gel the overshoe wall remains stored in the mold, meaningsimply that the mold does not cool instantaneously. The heat retained orstored in the mold is called the latent heat of the mold. It has beenfound that the gelling of plastic material 20 is caused by such latentheat, just as soon as it is poured into the mold. If desired, someadditional heat may be applied to add to or control the heat applied tothe plastic material. If no additional heat is applied, the thickness ofthe gelled sidewalls and base layer will be proportional d to the amountof latent heat in the mold and the time the plastic material 20 is leftin the mold.

Plastic material 20 is a plastisol of resin and plasticizer and in itscured form is more wear resistant than the plastic material of theovershoe 12 the former having a durometer hardness of 85, the latter, of70. It has been found that the plastic material of the overshoe shouldcontain from 60 to parts plasticizer for parts resin while plasticmaterial 20 should contain 35 to 40 parts plasticizer for 100 partsresin. If the plasticizer content of plastic material 20 falls below 35parts, the processing becomes extremely diificult; if it is above 40parts, the abrasion and stiffness characteristics of the reinforcingheel unit is adversely affected. Therefore, as used herein, the term aharder reinforcing plastisol means the plastisol used to form the heelunit 20 which is more wear-resistant than the plastic material of theovershoe and contains from 35 to 40 parts plasticizer for 100 partsresin. An example of a satisfactory compound is here given:

Reinforcing H eel Unit Compound Batch 52 2 5 Ingredients Base Lbs. ozs.

10.00 30 00 P-3038 (60 percent DiOctyl RhthalageAO percent Di-Octyldipate 19.00 57 0o swimmer (Butyl Phcnyl mas/um Phthalatc). 11.00 33 00Drapcx3f2 0ctylEpoxyStcarate). 3.00 9 00 Stabilizer .TCX (cadmiumorganic compound). 2.00 6 O0 Viscosity Depressing Agent-Sotex V. 100.00300 Polyvinyl Chloride Resin Mixing time: 30

minutes.

Since the viscosity of low plasticizer content plastisol is higher thanis allowable for the satisfactory operation of the hereindisclosedprocess, the viscosity being approximately between 10,000 to 20,000centipoises, a viscosity depressing agent must be added to the compoundto reduce the viscosity. That is, the viscosity of the compound afterthe depressing agent has been added must be between 2000 to 4000centipoises. It has been found that several types of viscositydepressing agents will do a satisfactory job; however, Sotex CW hasproved to be more effective. It has also been found that a satisfactoryplastisol (polyvinyl chloride resin) may be made of 70 parts Geon 121and 30 parts Goon 202. Further the cadmium organic compound used as astabilizer may be a cadmium ricinoleate or laurate. It should also benoted that the hardness and the viscosity of the heel compound may bevaried by performing steps, adding other compounds and substancesaccording to the practices well known in the art.

The names and addresses of the manufacturers of the components of theheel compound are here listed:

84 Chemical Corp.

Sotex CW: I

Synthetic Chemicals Inc.

335 McLean Blvd.

Paterson 4, NJ. Calchem Yellow:

Caledonia Co. Ltd.

751 Victoria Square Montreal, Quebec, Canada Polyvinyl chloride resin(Geon 202 and 121):

B. F. Goodrich Chemical Co.

3135 Euclid Ave.

Cleveland 15, Ohio After filling the heel cavity with plastic material,a suction tube 21 having positioning probes 22 is inserted into thecenter of the quantity of plastic and adjusted to a depth such that thebottom of the probes touch the bottom of the heel base and rest on theupper surface of the mold heel cavity. The correct position isillustrated in FIG. 3. The length of the probes determine the thickness18 of bottom layer 14. Of course, other means of positioning the suctiontube will occur to those skilled in the art.

A suction unit 23 is coupled to the suction tube at its opposite end andbegins to suck or draw up the viscous plastic after the suction tube isproperly positioned. The core portion of the plasticthe quantityimmediately around the suction tube is drawn otf first since the gelledlayer of plastic adhering to the sidewalls of the overshoe remains. Whenthe liquid level reaches the level of the bottom of the suction tube, asat 26, suction ceases. Thus the suction tube acts much like a straw inwater; when the water level is below the bottom of the straw, waterceases to move up the straw.

When suction ceases, the suction tube is removed, and additional heatmay be applied as shown in FIG. 4 to fix sidewall layer 24 and bottomlayer 27, in position. After layers 24 and 27 are fixed suificiently,the mold containing the overshoe is removed from heating unit 28 andagain enters the normal curing station where heat is applied to theentire mold containing the overshoe to cure the plastic of the overshoewall 12 as well as layers 24 and 27. Further, layers 24 and 27 becomefused or molecularly bonded to the overshoe wall during this curingstep. However, the step of applying heat by the external heating unit 28may be eliminated and complete fusion may be obtained in the finalcuring step by having sutficient heat in the curing oven.

While a preferred embodiment of the reinforced overshoe heel, and amethod for making same has been disclosed, it is not intended that theinvention be limited to such embodiment as many changes may occur tothose skilled in the art without departing from the essence of theinvention.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A method of forming a plastic overshoe having a heel portionseparately walled from the sole portion comprising the steps of pouringa quantity of plastisol into an overshoe mold, applying heat to the moldto gel a layer of plastisol adhering to the inner wall of said mold,removing the remaining liquid plastisol from the mold, pouring apredetermined amount of plastisol solely into said heel portion whileallowing the walls of said heel portion to serve as a mold While theplastic of the overshoe is gelled but before it is cured, applying aspecific degree of heat for a specific duration to gel the plastisoladjacent the base and sidewalls of said heel portion, removing theremaining liquid plastisol leaving only the base and sidewall layersthereof, and then curing the entire overshoe, whereby the overshoeplastic and the base and sidewall layers of plastic in said heel portionfuse forming a reinforcing heel base.

2. The method of claim 1 wherein the last-mentioned liquid plastisol isremoved from the heel portion by suction.

References Cited in the file of this patent UNITED STATES PATENTS1,536,866 Kamborian May 5, 1925 1,630,762 Randall May 31, 1927 1,896,123Schweitzer Feb. 7, 1933 2,142,981 Richard Jan. 3, 1939 2,237,835LHollier et al. Apr. 8, 1941 2,535,123 Demick Dec. 26, 1950 2,880,467Wibbens Apr. 7, 1959 2,915,788 Engel Dec. 8, 1959 2,923,029 Harris eta1. Feb. 2, 1960

1. A METHOD OF FORMING A PLASTIC OVERSHOE HAVING A HEEL PORTIONSEPARATELY WALLED FROM THE SOLE PORTION COMPRISING THE STEPS OF POURINGA QUANTITY OF PLASTISOL INTO AN OVERSHOE MOLD, APPLYING HEAT TO THE MOLDTO GEL A LAYER OF PLASTISOL ADHERING TO THE INNER WALL OF SAID MOLD,REMOVING THE REMAINING LIQUID PLASTISOL FROM THE MOLD, POURING APREDETERMINED AMOUNT OF PLASTISOL SOLELY INTO SAID HEEL PORTION WHILEALLOWING THE WALLS OF SAID HEEL PORTION TO SERVE AS A MOLD WHILE THEPLASTIC OF THE OVER-